Traditionally, print media has been the only way to record information and ideas. Thus, when a person annotated a paper version of a document, the annotation could be replicated, for example, by rewriting the annotation in another copy of the document or by making copies of the annotated document. Presently, advancements in digital imaging allow persons to convert documents in printed form into digital form. When a person annotates a paper version of a document, a digital version of the document can be made by physically scanning the annotated document into a digital form.
Conventionally, unique identifiers have been used to identify documents. A unique identifier can be a bar code, for example, that is exclusively associated with the document. Alternatively, a document may be identified by a watermark on a page that may be created by printing a unique background pattern as a document is being printed. When a person annotates a watermarked paper version of a document, the watermark pattern can be read by a machine to reveal the identity of the document. A watermark pattern on a page may also identify the location of the annotation in the document. However, a watermarking approach is not helpful when an annotated document exists on paper that was not previously watermarked.
Conventional approaches require a person to physically scan printed documents with annotations after the annotations are made and to use unique identifiers such as bar codes to identify the document. There remains a need for better technology for automatically correlating annotations of a paper document with a digital version of the document. The present invention addresses this need and other shortcomings in the prior art.